Burner and ignition controller with purging period



June 12, 1934. M E, H N G 1,962,506

BURNER AND IGNITION CONTROLLER WITH PURGING PERIOD Filed Nov. 30, 1931 Patented June 12, 1934 UNITED STATES PATENT OFFICE BURNER AND IGNITION CONTROLLER WITH PURGIN G PERIOD Application November 30, 1931, Serial No. 577,906

3 Claims.

An object of my present invention is to provide a purging period for a burner and ignition controller structure, the mechanism for accomplishing such purging period being comparatively simple, durable and inexpensive to manufacture.

A further object is to provide a purging feature for a burner and ignition controller of the type shown in my co-pending application, Serial No. 566,838, filed October 5, 1931.

More particularly, it is my object to provide in combination with a control device having a relay switch for a burner and an ignition switch for the ignition mechanism thereof, stack temperature actuated mechanism being provided for operating the ignition switch, a means to provide a purging period for the furnace in case of fire failure, comprising a circuit breaker in circuit with the relay coil of the relay switch and operable to open circuit position upon movement of the stack temperature actuated mechanism from hot stack position.

Another object is to provide the mechanism for operating the circuit breaker of such character that the circuit breaker is actuated immediately upon movement of tlie stack temperature actuated mechanism toward cold stack position, with the ignition switch moving to closed circuit position a period of time after opening of the circuit breaker.

A further object is to provide a novel form of lost motion connection to increase the purging period occurring between the opening of the circuit breaker and closing of the ignition switch by the stack temperature actuated mechanism.

With these and other objects in view my invention consists in the construction, arrangement and combination of the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawing, in which:

Figure 1 is a front elevation of a stack switch for controlling a burner and its ignition mecha nism, with the mechanism for providing-a purging period disclosed in connection therewith.

Figure 2 is a sectional View on the line 2--2 of Figure 1.

Figures 3 and 4 are views of elements in Figure 1 in different operating positions; and

Figure 5 is a diagrammatic view of a burner and ignition controller in connection with which my purging period mechanism is used.

On the accompanying drawing, I have used the reference numeral to indicate a switch housing from which the cover has been removed. A

relay switch housing is indicated at 12. housings 10 and 12 are supported on a hub 14 adapted to extend into the combustion chamber or stack of a furnace. An oscillatable rod 16 is supported by the hub 14 and a bimetallic coll 18 has one end secured thereto at 20 and its other end secured to the hub 14 at 22. It will be obvious that temperature changes within the stack into which the hub 14 is inserted will affect the bimetallic coil 18 to wind and unwind it according to temperature changes and thus impart osclllation to the rod 16.

Within the switch housing 10, a switch arm 24 is pivoted at 26. A bracket 28 is secured to the switch arm 24 and is provided with a slot 30 having depressions 32 and 34 at its upper and lower ends, respectively.

A link 36 has one end pivoted to an arm 38 which is operatively connected with the rod 16 by a slip joint connection.

The slip joint connection comprises a flanged hub 40 and a hub 42 secured to the rod 16 with a spring 44 interposed between the hub 42 and a washer 46. The lever 38 has a disk-like portion 48 interposed between the washer 46 and the flange of the flanged hub 40.

The other or lower end of the link 36 is provided with a plate-like enlargement 50 terminating in a pin 52 which is adapted to travel in the slot 30 and enter the depressions 32 and 34 during the operation of the control device.

The pin 52 is constrained to move into the clepressions 32 and 34 by a spring 56. The spring 56 is retained on the pin 52 by the terminal end 58 of the pin which is bent toward the right, as shown in Figure 1, the terminal end being omitted in Figure 3 and the pin shown in section.

The switch arm 24 is acted upon by the poles 60 of a magnet and carries contacts 62 and 64. The contacts 62 and 64 are adapted to coact with stationary contacts 66 and 68. The magnet poles 60 are provided to cause snap action of the switch arm 24. The contacts 62 and 66 are for controlling the ignition of the burner while the contacts 64 and 68 are for controlling a relay coil 84.

In my co-pending application hereinbefore referred to, a direct pivotal connection was substituted for the lost motion connection described by reference numerals 30, 32, 34, 50, 52, 56 and 58. Aside from the parts just enumerated, the device of my co-pending application included parts in Figure 5 which I will now describe.

A safety cut-out arm 70 is pivoted at 72 and constrained toward movement to open circuit position by a spring 74. The cut-out arm '70, however, is retained in closed position by a bimetallic latch '76 which may be unlatched manually by a button '78 or automatically by a heat coil'80. After being unlatched, the cut-out arm may be restored to latched position by a push button 82, providing the latch bar 76 is cool.

A relay coil 84 is provided for drawing spring opened contacts 86 into engagement with contacts 88 and 89 when the relay coil is energized. The relay coil 84 and the contacts 86, 88 and 89 are contained in the housing 12, while the parts 70 to 82 inclusive are contained in the housing 10. All of this construction, however, is shown only generally in the present application, it being fully disclosed in my co-pending application.

The wiring diagram, whereby the control device is connected with current supply, a room thermostat, a burner and ignition mechanism for the burner, is shown in Figure 5 and corresponds to the wiring diagram of my co-pending application. My mechanism for providing a purging or stand-by period for the furnace in the event that the fire goes out while the burner is operating, consists of the lost motion connection between the link 36 and the switch arm 24 and mechanism which I will now describe.

The switch arm 24 at its lower end is provided with a lateral extension 90. The extension 90 is adapted to coact with a thrust member 92 for separating a movable contact 94 from a stationary contact 96. The contacts 94 and 96 may be termed a circuit breaker for convenience in the description and claims.

The contacts 94 and 96 are included in the circuit of the relay coil 84, as shown in Figure 5.

The thrust member 92 is slidably supported by a bracket 98 and is provided with stop shoulders 100 and 102 to engage thereagainst. The thrust member also has a cam surface 104 which is retained in engagement with the bracket 98 by gravity. A corner 106 of the thrust member 92 is adapted to be engaged by the extension 90 of the switch arm 24.

l The end of the thrust member 92 opposite the corner 106 is provided with a strip of insulation 108 to prevent a short circuit between the contacts 94 and 96 and the switch arm 24. The strip 108 is adapted to engage a leaf spring 110 on which the movable contact 94 is mounted (see Figure 2). The leaf spring 110 is light and is carried by a heavier leaf spring 112. The leaf spring 112 is anchored at 114 and a set screw 116 is provided for adjusting its tension. The stationary contact 96 is carried by a bracket 118.

Practical operation thus energized, it acts upon an armature which draws the contacts 86 into engagement with the contacts 88 and 89. This causes operation of the burner which has an operating element such as an electric motor for operating the fuel pump and air fan or a magnetic fuel valve by the current flowing from terminal 1, through the burner to terminal 4, through terminals 88 and 86,

switch arm 70, contacts '71 and '73 and back to terminal 2 and also connects the lower end of the relay coil 84 with terminal 2, through contacts 89 and 86, switch arm '70 and contacts 71 and 73.

The stack switch is shown in cold position in Figure 5 so that the ignition circuit is established as soon as the room thermostat closes, such establishment being through the room thermostat from terminal 1, then through terminal 3 to the ignition mechanism and through terminal 5 to the ignition control contacts 62 and 66 from which the current flows through the switch arm 24, switch arm 70 and contacts 71 and 73 to current supply terminal 2. As the stack heats up, the switch arm 24 is moved, thus opening switch 66, 62 to break the ignition circuit and also opening switch 68, 64 to break the circuit through the heater coil so that it will not cause the latch '76 to unlatch the switch arm 70. The latch 76 is provided so that in the event ignition does not occur, it will unlatch the switch arm '70 to open the switch 71, '73 and thus de-energize all elements to shut down operation of the burner until such time as the trouble can be remedied and the controller reset for operation by pressing the button 82.

After the ignition is shut off, the burner will remain energized because even though the relay control contacts 64 and 68 have been separated, the relay coil 84 will remain energized because of the contacts 86 and 89 being in engagement with each other.

As soon as the circuit is broken by the room thermostat, the contacts 86 will be separated from the contacts 88 and 89 and as the stack cools down, the switch arm 24 will be moved to closed circuit position.

The foregoing description of the operation is normal. Sometimes, however, when the burner is in operation, the fire may go out because of any one of several reasons, such as a slug of water in the oil, a prolonged down draft from the chimney or a leaky suction line, etc. In such event, without the mechanism for providing a purging period which I have provided in my present application, the burner will continue to operate-that is, to force oil and air into the" furnace and as the stack switch cools down, the ignition contacts will come into engagement with each other, thus throwing on the ignition at a time when the furnace and stack are full of explosive gas. I will now describe the specific operation of the purging period mechanism.

It will be noted that the circuit breaker contacts 94 and 96 are so located that when the burner is operating and the stack switch is open because of the stack being hot, separation of the contacts 94 and 96 will break the holding circuit through the relay coil 84, thus allowing the spring opened contacts 86 to become separated from the contacts 88 and 89 and thereby breaking the circuit to the burner. When the burner is operating and the stack is hot, the parts are in the position shown in Figure 3, except that the circuit breaker contacts 94 and 96 are in closed position.

If the fire goes out, the stack temperature actuated mechanism from the coil 18 to the link 36 will immediately start operating, the link moving in an upward direction, as shown by the arrow a. The pin 52 at the Tower end of the link is held in the depression 34 by the spring 56 and thus the switch lever 24 is moved in the' direction of the arrow b which moves the thrust member 92 toward the right against the action of the light leaf spring 110, the parts then as-' suming the position of Figure 3. This separates the contacts 94 and 96, thus de-energizing the solenoid 84 for shutting down operation of the burner, as described in the preceding paragraph.

Further movement of the link 36 upward causes the left spring 110 to engage the heavier leaf spring 112, thus resisting the movement of the switch arm 24.

This causes the pin 52 to be pulled out of the depression 34, whereupon the circuit breaker contacts 94 and 96 will be reengaged, but will not energize the relay coil 84 because the relay control holding contacts 68, 89 were opened on deenergization of the relay coil 84 and contacts 64 and 68 in the initial operating circuit of the coil 84 are still spaced from each other. The pin 54 then continues to travel upwardly through the slot 30 as the stack becomes still cooler, thus providing a lost motion connection and resulting in a period of time between the opening of the circuit breaker contacts 94 and 96 and the closing of the ignition contacts 62 and 66 and the contacts 68 and 64 for the energizing circuit of the coil 84.

When the pin 52 engages the depression 32 at the upper end of the slot 30, the switch arm 24 will again be constrained toward movement in the direction of the arrow b against the action of the leaf springs 110 and 112 and the link 36 will continue to move upwardly, thus causing the cam 104 to raise the thrust member 92 to such a position that the corner 106 is above the upper edge of the extension of the switch arm 24. The extension 90 can then pass under the corner (Figure 4) and the switch arm 24 can be further moved to the closed circuit position of contacts 62, 66 and 64, 68 shown in Figures 1 and 2. Immediately after the position of Figure 4, the thrust member 92 will be returned to initial position (Figure 1) by the leaf spring 110.

Thus the burner is shut off as soon as the stack switch moves toward cold stack position by separating the circuit breaker contacts 94 and 96 and a purging period is provided while the pin 52 is traveling from the lower to the upper end of the slot 30, during which time the furnace can be purged of oil and air by the natural draft and after which the ignition contacts 62 and 66 and relay coil contacts 64 and 68 will be brought into engagement by the cooling of the stack for again operating the burner in a normal manner. Thereafter normal energization and de-energization of the burner and its ignition mechanism will continue automatically with the circuit breaker contacts 94 and 96 separating each time the relay coil is deenergized by opening of the switch contacts in the room thermostat, but this of course will have no efiect on the relay because it is dead at that time. The mechanism, however, is always in position for operation to provide a purging period in the event that the fire goes out while the burner is in operation.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may be reasonably included within their scope.

I claim as my invention:

1. A control system for an electrically operated burner mechanism having an electrically controlled igniter, said system comprising a relay switch mechanism for controlling the burner mechanism and operable to close a holding circuit for itself, and switch mechanism operable in response to combustion having three switches, an energizing circuit for the relay coil having therein a first of said switches, a circuit for the control of said igniter having therein a second of said switches, a third of said switches in both the energizing and holding circuits of the relay coil, said combustion switch mechanism being constructed to open said first and second switches only on successful combustion and on combustion failure to at least momentarily open said third switch a time period prior to reclosure of said first and second switches.

2. A control system for an electrically operated burner mechanism having an electrically controlled igniter, said system comprising a relay switch mechanism for controlling the burner mechanism and operable to close a holding circuit for itself, and switch mechanism operable in response to combustion having three switches, an energizing circuit for the relay coil having therein a first of said switches, a circuit for the control of said igniter having therein a second of said switches, a third of said switches in the circuit of the relay coil, said combustion switch mechanism being constructed to open said first and second switches only on successful combustion and on combustion failure to at least momentarily open said third switch a time period prior to reclosure of said first and second switches.

3. A control system for an electrically operated burner mechanism having an electrically controlled igniter, said system comprising a relay switch mechanism for controlling the burner mechanism and operable to close a holding circuit for itself, and switch mechanism operable in response to combustion having three switches, an energizing circuit for the relay coil having therein a first of said switches, a circuit for the control of said igniter having therein a second of said switches, a third of said switches for controlling the relay coil, said combustion switch mechanism being constructed to open said first switch and cause said second switch to de-energize said igniter only on successful combustion and on combustion failure thereafter to cause said third switch to de-energize said relay a time period prior to movement of said first and second switches to their initial positions.

MALCOLM E. HENNING. 

